The use of centrifugal pumps having a motor which is connected directly to the solar cells has become known heretofore; such pumps require a minimum rotation for operation thereof, to be able to maintain manometric pressure without which the pump does not pump. This minimum rotation of the driving motor requires a supply of a constant amount of electric power to be able to pump a liquid above the manometric pressure of the system. During periods of low level of solarization, the operation of the motor-centrifugal pump unit must be assured, making it necessary to resort to a great many solar cells. In driving centrifugal pumps, a d-c motor is used which, when connected to the solar cells, present the disadvantage of not permitting the transfer of the entire electric energy available in the solar cells outside the insulation peaks. This happens because the electric d-c motor has an apparent resistance proportional to the speed of rotation thereof, and when the electrical energy furnished by the solar cells is not maximum (periods of low level of solarization), the speed of the motor will be lower, therefore presenting also a lower apparent resistance which is in series with the internal resistance of the solar cells, causing the generated electric power to be partially dissipated in the solar cells with consequent decrease in yield of the system. Also known heretofore is the use of chemical accumulators of electrical energy, which store the energy generated by the solar cells, the accumulators driving an electro-mechanical system for pumping liquids.
Because of the technical drawbacks set forth, the high costs of the low-yield systems in use, the liquid pumping systems employing solar energy are restricted to low manometric pressures, the task of the invention of the instant application being to offer a better technical solution without the stated disadvantage, a better yeild and greater economy.